08 June 2011

Australian government deliberately underestimating risks from rising sea levels

First published in Crikey, 8 June 2011

Last weekend, the Australian government released the latest in a series of reports documenting the possible impacts of climate-change-induced sea-level rises (SLRs) on Australia.

It found a "worst-case scenario sea level rise of 1.1 metres" within 90 years would have a devastating impact, with as much as $266 billion worth of potential damage and loss to buildings and infrastructure.

This upper bound of 1.1 metres is used consistently by government. Inundation maps use three simple sea-level rise scenarios for the period about the year 2100: low (0.5m), medium (0.8m) and high (1.1m).

The big problem is that 1.1 metres is the wrong figure by a wide margin, with serious implications for the efficacy of the risk management and planning such research should underpin.

In releasing an earlier report, Senator Penny Wong told ABC Insiders on November 19, 2009 that "1.1 metres … is about the upper end of the risk". But the report said:
"Recent research, presented at the Copenhagen climate congress in March 2009, projected sea-level rise from 0.75 to 1.9 metres relative to 1990, with 1.1–1.2 metres the mid-range of the projection. Based on this recent science 1.1 metres was selected as a plausible value for sea-level rise for this risk assessment".
So a mid-range projection from the government’s own report in 2009, based on the peer-reviewed science, transmuted into a peculiar creature, a "plausible value", and now two years later "is about the upper end of the risk", which the Department of Climate Change knows to be wrong, as the literature also demonstrates.
  • Pfeffer, et al. in Science conclude "an improved estimate of the range of SLR to 2100 including increased ice dynamics lies between 0.8 and 2 metres."
  • Vermeer & Rahmstorf in Proc. Natl Acad. Sci. USA estimated a sea-level rise of 0.75–1.9 metres by 2100.
  • A new report from Arctic Monitoring and Assessment Program finds "Global sea level is projected to rise 0.9 to 1.6 metres (3.0 to 5.3 feet) by 2100."
  • A recent survey of sea-level-rise forecasts by Nicols et al. in "Philosophical Transactions of of the Royal Society A." summarises the findings in this graph:

As Ross Garnaut has noted, climate science projections have sometimes been reticent when compared to observations. The 2007 IPCC report excluded the impact of melting ice-caps from its now-obsolete sea-level figures, and recent satellite data shows Antarctica and Greenland losing ice mass at an increasing (and possibly exponential) rate.

Dr David Carlson, director of the International Polar Year Program, says a "very plausible outcome" is a metre or more of sea level rise in this century from Greenland alone. And the West Antarctic glaciers also appear particularly vulnerable.

So what difference would a metre make? A huge amount. The damage to buildings and infrastructure impacted by a 2-metre rise and associated storm surges is likely to be more than double the $266 billion figure established in the recent report, and it seems extremely foolish to neither recognise that possibility nor plan accordingly.

Sensible risk management requires an assessment of the full range of possible outcomes, their impacts and consequences; not the average. By not doing so, the government is failing in its fiduciary duty. Communities and business, infrastructure authorities and local government planners are relying on the government’s assessment of sea-level rise risk to plan their future and make contingency plans.

By simply ignoring the available science and failing to assess the risk associated with the full range of possibilities, the government may leave itself open to huge litigation should reality turn out to be closer to the scientists’ upper bound that the government’s "plausible value".

Or perhaps we can leave it all to Senator Ron Boswell, who told an estimates hearing in February: "Being someone who has spent his life in boats, since I was a kid, I haven't seen any sea level change."


  1. Of course the sea level doesn't change. Heights above sea level are measured.... above sea level. Which means that actually the land is sinking. Now all we need to do is to fund an expedition to find the giant plug at the bottom of the ocean to let the water out and we'll all be right!

  2. Given the report on the arctic sea ice death spiral last week, I would have thought that 2 metres by 2050 is now on the cards, and besides I cannot see that cities as we know them will be worrying too much about the sea coming up when they are suffering shortages of food and energy and medicines and other extreme climatic developments.

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  4. James Hansen et al in new papers say:

    "The most reliable indication of the imminence of multi-meter sea level rise may be provided by empirical evaluation of the doubling time for ice sheet mass loss. Mass loss by the Greenland and Antarctic ice sheets can be deduced from satellite measurements of Earth's gravity field. Fig. 8 shows mass loss reported by Velicogna (2009). The most important curves are the 12-month running means of the annual mass change of the Greenland and Antarctic ice sheets (heavy blue lines in Figs. 8c and 8d), which average out the annual cycle. These data records are too short to provide a reliable evaluation of the doubling time, but, such as they are, they yield a best fit doubling time for annual mass loss of 5-6 years for both Greenland and Antarctica, consistent with the approximate doubling of annual mass loss in the period 2003-2008. There is substantial variation among alternative analyses of the gravity field data (Sorensen and Forsberg, 2010), but all analyses have an increasing mass loss with time, providing at least a tentative indication that long-term ice loss mass will be non-linear. We conclude that available data for the ice sheet mass change are consistent with our expectation of a non-linear response, but the data record is too short and uncertain to allow quantitative assessment. The opportunity for assessment will rapidly improve in coming years if high-precision gravity measurements are continued."

    SLR from Greenland and Antaarctic over last decade has been 1.5mm/year approx.

    If doubling time is 10 years, than yields about 1.5 metres to 2100 plus thermal expansion.

    If you take a more conservative 1mm and take doubling time of 8 years, than yields about 4 metres to 2100 plus thermal expansion (at least 1m), which was Hansen's ballpark of 5 metres from 4-5 years ago when he was writing about scientific reticence and sea-level rises.